Method of refining lead



May 4 1926.# 1,583,495

y n I H. mscHLEjcHER METHOD o'F REFINING- LEAD n Filed Nov. e I 1925( w. 51MB@ y ATTORNEYS Patented May 4, 192.6.

(UNITED ASTATES] y PATENT oFF1cE.-

HENRY M. soHLEIcHER, '0E MONTERREY, MEXICO, As'sI'GNoRTo AMERIGAN METAL COMPANY, LTD., oF'NEW YORK, N.

` Y.,`A coRroRATIoN or NEW"` YORK.

1 METHOD OEREEINING LEAD., 1,

Appiicatin med 'November e, 19251.-4 IserialA No. 67,223.

To all whomima-y/ con-ocra:

Be it known that I, HENRYM.; Scrinnicrlrny' a citizen of the United States, residing at,

Monterrey, Nueva- Leon, Mexico, have in- `vented certain new and.` useful Improve-y vmentsin Methods of ARefining Lead; and I. 'L do 4hereby declare the following to `be a full,

clear, and exact descriptionsof theinvention,

such aswill venable others skilled in the.art to which it appertains toQmake and use, the,

same.

This rinvention relates to V,a methodof reninglead, and particularlyto the removal of elements such as arsenic, antimony, tin

Thel method 'depends upon .the selectiyel oxidation of impurities,` usually arsenic, antimony, tin and zinc, and the absorptionof the oxidized elements by the alkalimetal hydroxide. heretofore has been carried out in' a noncontinuous manner, the alkali -metal hydroxide being disposedupon the surface of the lead bath, either in a partially immersed cylinder or otherwise .and Ipermitted to, remain until it has absorbed the desiredgpro-v portion of the oxidized impurities. .When

. the alkalifnietal hydroxide has absorbed the impurities to the extent which is .advisable in view of the subsequent treatment, it is*L usual to replace. it with fresh alkali metal' hydroxide and to repeat the operation until the desired purification is accomplished. This point inthe operation is hereinafter called saturation.l The ,method when so, conducted 'is `relatively slow because of .the necessity for `rctardii'ig the reaction as the purification approaches the nishing stagel eithernwith reference to the saturation 'ofthe alkali ymetal hydroxide or of thedepletion of theimpurities in the lead. V Care must be taken to avoid going too far in either direction. Furthermore, tlie-operation-of' the method depends upon the oxidation .of the" load and the subsequent oxidation of the im-l purities vby the lead oxide. The impure-lead oxidizes less readily than lead from which the impurities have been removed substantially. Consequently t-he maximum rate of has beenv accom- The operation as conductedv undeithe lconditions mentioned.y

remoifalof the impurities cannotbe attainedk It isithe object of the inventionv to provide` a method of purifying lead which is more kand the selective Aseparation of several impurities if s uch arepresent.

Lvention will be apparentas it is better .undervstood byv reference to the, following :specirapid .and satisfactory 'in ,operation andy which is adaptable forcontinuous operation Furthery objects and advantages of the in- Uication and to the accompanying-drawing iii which a suitabletype of apparatus for the practice of the methody is, illustrated diagraiiim'atically. In the drawing,l y y m f Fig. l1 isa sectionalfviewof a type ofii' apparatus adaptedL for *the removal of a single element or of theV several impurities.

together-forin succession; y

Fig. `2` is asimilar. vien7 illustrating the apparatus in .which .the impuritiesv are fremoved separately; and

3 ind'cates the apparatus for counter-current` operation.

In starting. the refining; operation I .em-

ploy instead-of a bath of the impure lead,y

one from'which the impurities have-,been y removed. ,This ensures ,the most active oxidation and facilitatesl the` .removal ofA the impuritiesfromlthe lead which is addedv continuously tothe bath. Thus, as a simple bat-h may contain less than .01% of ant-imony if nosilveris present, or about .01% of antimony iffthe lead is to be desilverized subsequently. iIt is assumed for the, purarsenic, tinl and` zircf are absent. f To this bath the impure lead. containing a considerablyvlargicrvproporton of antimony, is fed continuously at aprat'e corresponding to the ratc ofremoval of the antimonytherefrom.y

At the Sametime a corresponding amount of thep'uritied lead-is withdrawn continuously andpreferably from the bottom of thel bath.y For this purpose the vessel in example of the operation; the lead in thev vpose of simplifying the explanation that',A

which the lead bath is maintained can bey Siphon so that a constant Vquantity of the metal is retained therein. A Siphon is preferable because it will draw oli the lead from the bottom of the vessel Wherethe purest lead tends to settlein a layer because of its greater specific .gravity.

provided with a suitableoutlet such as a,

The purification is accomplished bythe action of a suitable reagent such as an alkali metal hydroxide or a mixture thereof with common salt in the presence of an oxidizing agent. -The alkali metal hydroxide or mixture can be disposed so as to contactwith the surface of the molten metal and particularly to be engaged by the impure metal which is introduced to the bath. Preferably the impure metal is fed directly to the al-. kali metal hydroxide or mixture and the molten lead in the bath is circulated by means of a pump .-.o that it passes successively therethrough. The oxidation may be caused by atmospheric air which is blown or otherwise introduced to the bath of molten metal.` Alternatively oxidation depends upon the introduction of an oxidizing salt such as an alkali metal nitrate. In the presence of the oxidizing avent the lead is partially oxidized and the lead oxide produced is carredinto contact with the impure metal and the alkali metal hydroxide or mixture. The lead oxide oxidizes the impurities in the impure metal and the oxidized impurities are absorbed by the alkali metal hydroxide or mixture'so that the impurities are progressively separated and the amountof impurities present in the lead of the bath remains substantiallyy constant. If a singlebody of the reagent is used it will be necessary to delay the operation when it approaches the finishing stage. viding two separate bodies of the reagent one can be removed and replaced while the other'vis being utilized in the continuation of the operation. Alternatively, the reagent can be introduced continuously in the proper proportion to maintain a substantial- -y -constant saturation with. the impurities at a point where the reaction is active and the corresponding amount of the reagent containing the impurities `can be withdrawn continuously,

yAs the result of the operation as described the impure lead containing antimony is supplied to the bath at a constant rate and the purified lead containing an amount of antimony corresponding to that originally in the bath is removed continuouslyv from the bottom thereof. This permits the refining of the lead to the desired purity rapidly and 5 eiciently, the operation being particularly effective because of the fact that the pure lead oxidizes rapidly, ensuring consequently the necessary amount of lead oxide to re-v move the impurities from the impure lead which enters the bath. Excessive saturation of the reagent is likewise avoided so that the operation isv not delayed during any period. o

The invention may be applied to the successive removal of arsenic, antimony, tin and zinc from the lead. lThese elements can be removed in the same receptacle by maintaining suitable oxidizing conditions but preferably a series of receptacles are used, each being provided with the necessary reagent and being connected in such a manner that the lead will flow' through the receptacles in succession. The receptacles will be filled in initiating the operation with lead containing onlyv the impurities which are intended to remain therein at the termination of the purification in that receptacle. Thus, for example, in the rst receptacle the lead will contain antimony and tin but no arsenic. The second will vcontain antimony but no tin or arsenic yand the third a minimum amount of antimony. In conducting the operation the impure lead is fed to the lirst receptacle, and after purification therein it flows into the second recep-` tacle and finally into the third where the purification is completed. If desired the necessary reagent and the oxidizing material are fed to each of the receptacles and a corresponding amount of the impure reagent can be withdrawn from these receptacles,v thus permitting operation in a continuous manner. It is obvious that the rate of`removal of the several impurities will vary, and in operating with successive receptacles as indicated the' rate of flow of the metal must be adjusted to the rate ofv elimination of the'impurity which is relm-oved most slowly. The rate of oxidation in the other receptacles is then adjusted to ensure removal of the. respective impurities.

In purifying hard lead, that is, lead containing antnnony which should not bc revmoved, the method of operating `Would in volve the provision of two or more baths of antimony and lead, each with provision for the introduction of the necessary reagent and oxidizing material. Impure hard lead and the fresh reagent are continuously added in such a manner as to permit countercurrent passage through the system, that is`to say, the lead flows in one directionwhile the reagent flows inthe other'. In this casc the alkali metal nitrate or other oxidizing agent is introduced to the system only at the `place where the fresh reagent is added. Any antimony which is oxidized and absorbed by the reagent tends `to be reduced again by the other impurities in the successive receptacles and thus reenters the lead.. The same procedure can be employedl also with advantage when the lead contains a single impurity whichis to be removed or where two or more impurities are removed in a single operation.

Referring to Fig. l of the drawing, a kettle 5 may bc supported in a suitable furnace to permit the maintenance of the lead bath 6 contained therein at the required temperature. A receiver 7 is supported so that its lower edge is beneath thesurface of the bath of molten metal, the receiver being adapted to contain the reagent 8 which rests upon the surface of the lead bath and is thus prevented from escaping. A pump 9 of any suitable kind adapted to handle the molten metal is disposed'beneath the surface of the batti and is provided with a delivery pipe 1U through which the metal is` fed tothe lreceiver so that it falls throughv the reagent therein. Fresh reagent can be supplied through a conduit 11. "A siphon 12 is airanged to Withdravvmetal from the lower part of the bath and to deliver it to a suitable receptacle 13. The lead originally' present in the 'kettle 5 should, as above in.

dicated, have the composition of the desired product, being free, for example, from arsenic and tin and ha ving the minimum proportion of antimony. The impure lead con taining the antimony to be removed is introduced at the desired vrate through a con vduit 14 to the reagent 8, and if desired a supply of the reagent can be introduced similarly through the conduit 11. If the reagent is supplied continuously an overflow 15 permits the continuous Withdavval of aportion of the reagent containing the impurities. The reagent used may be an alkali metal hydroxide or a mixture thereof With common salt (sodium chloride) with or Without the addition of an oxidizing agent such as an alkali metal nitrate. Va-y rious other chemical compounds and mixtures thereof` can be utilized for the purpose of the invention. Air can be introduced to `the bath by any suitable means. As the operation proceeds a portion of the relatively pure lead in the bath is oxidized and the lead oxide in turn oxidizes the impurities present in the lead 'which is fed con tinuously to the bath. The rea-gent absorbs these oxidized impurities. If' the reagent is supplied continuously itl can be maintained at the desired concentration with respect to the impuritiesv by the .contlnuous withdrawal cfa portion of the reagent.

Otherwise it is desirable to employ two o1 more bodies of the reagent, one of which is operative While the other is being removed.

In Fig. 2 of the drawing a series of kettles 16, 17 and 18 are adapted to be maintained at the desired temperature by suitable furnaces provided for that purpose. Lead is Withdrawn' from the kettle 16 through a Siphon 19 provided for that purose and is delivered to the kettle 17 and the livered through a Siphon 20 to the kettle 18. It is finally Withdrawn through a siphon 21 1nto a receptacle 22 Which is provided to receive the purifiedinetal. Each of the kettles is provided with a receiver 23 for the reagent and a pump 24 in each of the kettles forces the molten metal upwardly through a pipe 25 and into the receiver. The inipure lead is delivered to the `receiver in the kettle 16 by a conduit 26 and passes throug'iil y the several kettles in succession as indicated. Fresh rea-gent can be added to the receivers in each of the kettles or it can be added to the .receiver in the last kettle and conveyed thereafter through the other receivers suecessively. `As an example ofv the operation arsenic can be removed'in the kettle 16, tin in the kettle 17 and antimony in the kettle i8. In starting the operation the lead in each of the kettles should have the composition With respect to impurities which is to be attained by purification therein. Thus the lead in the kettle 18 Will contain the minimum amount of antimony and lead having this composition can be Withdrawn c'ontinuously from this kettle.

In Fig. 3 of the drawing the arrangement of the kettles for counter-current operation is indicated. -'I`he kettles 27', 28'and 29 may be disposed' in the relation indicated with receivers 30 therein -to hold the reagent. The fresh reagent is introduced to the receiver 30'in the kettle 27 and the impure lead is introduced to the' receiver 30 in the kettle 29. The purified llead is Withdrawn then from the kettle 27 and the reagent saturated With the impurities is Withdrawn from the receiver 30 y, in the kettle 29. The molten lead and the reagent are transferred between the kettles and receivers therein in the manner indicated by the arrows so that these materials travel in counter-current relation. It is to be understood, of course, that each oi' the kettles is provided with a vpump tociiculate the molten metal and that siphons or other means may be employed to transfer the metal and the reagent as required.

The reagent recovered from anyof the operations asdescribed contains the impurities originally presentin the lead and these impurities constitute valuable products. The reagent can be treated suitably for the recovery of the several impurities, the operation being so conducted as to regenerate alkali metal hydroxide or other materia employed, as -the reagent. f

From the foregoing description the principles of the operation of the method will be understood. The efliciency of the method depends upon the more rapid oxidation which is accomplished under the conditions mentioned and the maintenance of the reagent at such a concentration with reference to the several impurities that the most effective absorption thereofis assured. "While the operation is conducted preferably as hereinbefore indicated, the principles thereof may be applied in a variety of Ways depending upon the nature and proportion of the impurities which are present in the lead. f The absence of one or more of the impurities mentioned will obviate the necessity of the particular step involved in its removal. Similarly the rate at which the lead is permitted to flow through the apparatus and the oxidizing conditions mentioned must be varied in accordance with the proportion of that impurity which is removed least rapidly by the puritying operation. Likewise various changes can be made in the apparatus employed without' departing from the invention or sacrificing any or' the advantages thereof.

I claim:

l. The method of refining lead, which comprisesY maintaining a bath of molten lead, which is substantially free from the substance removed as impurities, in contact with a reagent capable ot absorbing the oxidized impurities and in the presence of an oxidizing agent, and adding `lead containing iinpurities to be removed' to the bath at substantially the rate of absorption of the oxidized impurities by the reagent.

2. The method of refining lead, which comprises maintaining a bath of molten lead, which is substantially free from the substance removed as im1 urities, in contact with a reagent capable of' absorbing the oxidized impurities and in the presencev of an oxidizing agent, adding lead containing impurities to be removed tothe bath at substantially the rate of absorption of the oxidized impurities by the reagent and withdrawing the purified lead from the bath at an equivalent rate.

3. The method ot refining lead, which comprises maintaining a bath of molten lead, which is substantially :tree from the substance removed as impurities, in contact with a reagent capable of absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing impurities to be removed to the bath at substantially the rate of absorption of the oxidized impurities by the reagent and supplying the reagent so as to maintain a substantially const-ant concentration of the impurities therein.

4. The method of refining lead, which comprises maintaining a bath of molten lead, which is substantially free from the substance removed as impurities, in contact with a reagent capable of absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing impurities to be removed to the bath at substantially the rate-of absorption ot the oxidized impurities by the reagent, supplying the reagent so as to maintain a substantially constant concentration of the impurities therein and withdrawing a portion ot the reagent containing the impurities.

5. yThe method of refining lead, which comprises maintaining a bath of molten lead, which is substantially Jfree from the substance removed as impurities, in contact with a reagent capable ot absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing impurities to be removed to the bath at Substantially the rate ot' absorption of the oxidized impurities by the reagent and circulating the molten lead through the reagent.

G. The method of refining lead, which comprises maintaining a bath of molten lead, which is substantially free from the substance removed as impurities, in contact with .a reagent capable'ot absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing impurities to be removed to the bath at substantially the rat-e of absorption of the oxidized impurities, circulating the molten lead through the reagent and withdrawing the puried lead i'rom the bath in proportion to the amount ci impure lead added thereto.

7.y The method of refining lead, which comprises maintaining a bath of molten lead, which is substantially free from the substance removed as impurities, in contact with a reagent capable of absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing im purities to be removed to the bathat subtantially the rate of absorption of the oxid`zed impurities, circulating the 'molten lead through the reagent, withdrawing the purified iead, from the bath in proportion to the amount of impure lead added thereto and supplying the reagent so as to maintain a substantially constant concentration of the impurities therein.

S. The method ot refining lead, which comprises maintaining a bath of molten lead, which is substantially free from the substance removed as impurities, in Contact with a reagent capable of absorbing the oxi- 'dized impurities and in the presence of an oxidizing agent, adding lead containing impurities to bel removed to the bath at substantially the rate of absorption of the oxidized impurities, circulating the molten lead through the reagent, withdrawing the purified lead from the bath in proportion tothe amountV of impure lead added thereto, supplying the reagent so as to maintain a substantially constant Concentration of the impurities therein and withdrawing a portion of the' reagent containing the impurities.

9. The method of Arefining lead, which comprises maintaining a series of baths of molten lead, each of which is substantially free from the substance removed as impurities in the respective bath, in contact with a rea-gent capable of absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing impurities ties in the respective bath. in contact with a reagent capable ot absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing impurities to be remoued to the iirst bath of the series, conveying the lead progressively through the series of baths and supplying the reagent so as to maintain a substantially constant'. concentration otl the impurities therein.

11. The method ot refining lead, whichv comprises maintaining a series of baths ot' molten lead, each ot which is substantially free from the substance removed as impurities in the respective bath. in contact with a reagent capable of absorbing the oxidized. impurities and in the presence of an oxidizing agent, adding lead containing impurities to be removed to the first bath otv the series, conveying the lead progressively through the series of baths, supplying ,fresh reagent to the last bath ot the series and conveying it progressively through the preceding baths in counter-ein'rent relation with the lead. y

12. The method of reiining lead, Which comprises maintaining a series of baths ot' molten lead, each of which is substantially free from the substance removed as impurities in the respective bath, in contact with a reagent capable of absorbing the oxidized impurities and in the pre-sence ot au oxidizing agent, adding lead containing impurities to be removed to the first bath of the series, circulating the lead through the reagent in each bath, and .conveying the lead progressively through the series of baths.

13. The method of refining lead, which comprises maintaining a series of baths of molten lead, each of which is substantially `free from the substance removed as impurities in the respective bath` in Contact with a reagent capable ot' absorbing the oxidized impurities and in the presence of an oxidizing agent., adding lead containing impurities to be removed -to the first bath of the series, circulating` the lead through the reagent in eaeh bath. tonveying the. lead progressively through the series ol baths and supplying the reagent so as to maintain a substantially constant concentration of the impurities therein.

lli. The method oit refining lead, Which comprises maintaining a series ott baths of molten lead, each otivhich is substantially free t'rom the substance removed as impurities in the. respective bath, in contact with a reagent capable ot absorbing the oxidized impurities and in the presence of an oxidizing agent, adding lead containing'impuritiesl lto be. removed to the iirst bath of the series,

circulating the lead through the reagent in each bath. conveying the lead progressively through the series ot baths, supplying fresh reagent to the last bath of the4 series and` conveying it progressively through the preceding baths in counter-current relation Wit-h the lead.

1,5. The. method of refining lead, which comprises maintaining a bath of molten lead containing impurities in the proportion desired i n the final product, continuously adding impure lead to the bath and Withdrawing the product therefrom and removing the impurities to the desired degree by circulating the lead in contact with a reagent capable of absorbingV the oxidizedimpurities in the presence ot an oxidizing agent.

- In testimony whereof I affix my signature.

HENRY M. SCHLEICHER. 

